The field of art to which this invention pertains is fluid particle cooling. It particularly relates to the combustion of combustible material or stripping of strippable material from a particulated solid such as fluidizable catalyst which has been contaminated by the deposition thereupon of the combustible or strippable material, coke. The present invention will be most useful in a process for regenerating coke-contaminated fluid cracking catalyst, but it should find use in any process in which combustible material is burned or strippable material is stripped from solid, fluidizable particles.